Windows 10 21H1, aka the ‘Spring Update,’ is slated for release within the next two months. Microsoft has announced that the Spring Update will be released using an enablement package that simply turns on dormant features already found in Windows 10 2004 and Windows 10 20H2. For users running older versions of Windows, you will need to install a far more significant update, likely greater than 2GB in size, that will take quite a bit longer to download and install. Users should still upgrade to Windows 10 as there could be under-the-hood improvements that enhance security and Windows performance.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-spring-update-the-new-features-and-how-to-download/